Rotary disk valves are well-known in the art, and are comprised of a valve disk that is carried by a rotatable shaft. More commonly, the central axis of the shaft extends in, or parallel to, the central plane of the valve disk, but, this is not essential to such a rotary disk valve construction.
U.S. Pat. No. 5,095,946, McLennan, issued Mar. 12, 1992, teaches a disk valve construction in which a composite disk valve is positioned with the central plane of the valve disk extending at an angle to the longitudinal axis of the valve shaft. In that patent, the disk valve specifically is formed at a two-part construction, as is the housing for the disk valve, thus allowing for closure and sealing of the respective halves of the housing by the respective halves of the disk valve prior to separation of the two halves of the housing from each other, thus to provide a dry break coupling.
In the case of the commonly known disk valve, which may have, but does not essentially require an elastomeric seal extending peripherally of the valve disk, the requirement arises that the periphery of the valve disk must be kept free of debris and particulate matter as it moves onto the associated valve seat, especially when the valve is to be employed in pipe lines carrying abrasive slurries. The presence on the edge of the valve disk of abrasive particles can result in leakage past the valve disc, and also result in leakage past the valve disc, and also result in abrasion and scouring of the edge of the valve disk, or, abrasion and scouring of the valve seat with which the valve disk cooperates, and, eventual decrease in the sealing effectiveness of the valve.
While these considerations also can apply in the construction of U.S. Pat. No. 5,095,946, a further and more pressing requirement is present, that being, prior to separation of the valve halves, the requirement to wipe contaminants from the surface of an elastomeric seal that extends peripherally of the valve disk, the liquid contaminants envisaged being of a highly flammable and potentially explosive nature, or other noxious fluids.